In a turbine engine, there are numerous instances in which a stationary component is positioned in close proximity to a rotating component. Severe consequences can arise if these substantially adjacent components come into contact with each other. One area of concern is in the compressor section of a gas turbine engine.
An example of a compressor section is shown in FIG. 1. The compressor section 10 can be housed within a casing or shell 12. The outer casing 12 can be made of two generally semi-cylindrical halves that can be secured together. The outer casing 12 encloses, among other things, a rotor (not shown) having a plurality of disks 14 that extend radially outward therefrom. A plurality of airfoils or blades 16 can be mounted on each disk 14 to form a row. The rows of blades 16 alternate with rows of stationary airfoils or vanes 18. In some instances, the vanes 18 can be provided in the form of a diaphragm 20. Each diaphragm 20 can include inner and outer radial bands 22,24, known as shrouds, with a plurality of vanes 18 circumferentially arrayed therebetween. Like the compressor shell 12, the diaphragm 20 can be made of two substantially semi-circular halves. The diaphragm 20 can be attached to and extend radially inward from the compressor shell 12. For example, the compressor shell 12 can include a circumferential slot 26 along its inner peripheral surface 25 for receiving the outer shroud 24 so as to attach the diaphragm 20 to the shell 12.
As is known in the art, a seal holder 28 can be attached to the inner shroud 22 of the diaphragm 20. One or more seals 30 can extend from the seal holder 28. One or more surfaces of the seal holder 28 can be in close proximity to one or more surfaces of the rotor disk 14. During engine operation, the seal holder 28 and the rotor disk 14 should be spaced from each other; however, contact 32 between the seal holder 28 and the neighboring rotor disk 14 has been known to occur, as shown in FIG. 2. Serious damage can result if portions of the seal holder 28 liberate and travel through the compressor 10.
Prior attempts at detecting such contact in advance have included the use of proximity sensors to measure the distance between the seal holder 28 and the rotor disk 14. While providing continuous measurement of the distances between the seal holder 28 and the rotor disk 14, such sensors are impractical for general application because they require wiring to be run from outside of the casing 12 down to the seal holder 28. This wiring must be routed down the axial downstream side of the compressor diaphragm vanes 18.
The durability of the wiring is doubtful in such an environment. In addition, the presence of the wiring can degrade the performance of the compressor. Further, multiple sensors may be required for each compressor row; in the event of a sensor failure, replacement of a failed sensor would be time-consuming and costly. Thus, not only is there a need for a system that can provide advance warning of contact between a stationary component and a nearby rotating component, but there is also a need for a system that can detect such contact remotely so as to avoid the need to have wires extending inside of the compressor.